Our current understanding of atmospheric mercury lacks fundamental details. Gas phase elemental mercury (Hg°) was measured aboard the NASA DC-8 research aircraft during the Intercontinental Chemical Transport Experiment-Phase B (INTEX-B) conducted in spring 2006 over the North Pacific. Our data confirm efficient chemical cycling of Hg° in the tropopause region and show that it is strongly anti-correlated with O3 there, yielding a tropospheric-stratospheric mixing curve of ∼−0.20 ppqv Hg°/ppbv O3. In addition, we found frequent total depletion of Hg° in upper tropospheric (8–12 km) air masses impacted by stratospheric influence. When O3 mixing ratios were >300 ppbv, Hg° was rarely detected. It appears that in the tropopause and stratosphere Hg° is oxidized on the order of days followed by heterogeneous transformation to particulate mercury. These processes constitute an effective chemical sink for Hg° at the top of the troposphere, which may recycle mercury back to the gas phase as stratospheric aerosols are eventually dispersed into the troposphere.
Geophysical Research Letters
Digital Object Identifier (DOI)
Talbot, R., H. Mao, E. Scheuer, J. Dibb, and M. Avery (2007), Total depletion of Hg° in the upper troposphere–lower stratosphere, Geophys. Res. Lett., 34, L23804, doi:10.1029/2007GL031366.
Copyright 2007 by the American Geophysical Union.